Repetition rate locked single-soliton microcomb generation via rapid frequency sweep and sideband thermal compensation

Dissipative Kerr solitons (DKSs) with mode-locked pulse trains in high-Q optical microresonators possess low-noise and broadband parallelized comb lines, having already found plentiful cutting-edge applications. However, thermal bistability and thermal noise caused by the high microresonator power and large temperature exchange between microresonator and the environment would prevent soliton microcomb formation and deteriorate the phase and frequency noise. Here, a novel method that combines rapid frequency sweep with optical sideband thermal compensation is presented, providing a simple and reliable way to get into the single-soliton state. Meanwhile, it is shown that the phase and frequency noises of the generated soliton are greatly reduced. Moreover, by closing the locking loop, an in-loop repetition rate fractional instability of 5.5 x 10(-15) at 1 s integration time and a triangular linear repetition rate sweep with 2.5 MHz could be realized. This demonstration provides a means for the generation, locking, and tuning of a soliton microcomb, paving the way for the application of single-soliton microcombs in low-phase-noise microwave generation and laser ranging. (C) 2022 Chinese Laser Press

Automated summary

In this research, a novel method combining rapid frequency sweep with optical sideband thermal compensation is proposed to achieve stable generation of single-soliton state and significantly reduce phase and frequency noise. The study also demonstrates high stability of repetition rate and linear scanning achieved by closing the locking loop. This research provides important methods and directions for the generation and application of single-soliton microcombs.